When playing EMC levelsets, I've noticed a few issues with the artwork:
• Graphics are defined to EM Exit, but sounds are defined to RND Exit.
• There are only two kinds of Steel Wall defined. (EMC uses 3)
• There is only one kind of Slippery Wall defined. (EMC uses 2)
• Even though Letter "Copyright" is defined, it's never actually used. (Levelsets instead use Wall 8)
• The Android's diagonal movement graphics are in reverse order. (It's "entering space" animation is its "leaving space" animation, and vice-versa)

I've done some tests with the Emerald Mine Club level collection (version 2.1.1, which is the one you can download from the "Levels & Artwork" page) using the very first level set (Ace Mine 1) and the level editor (to directly test the issues), and I have some questions about your observations:

• Graphics are defined to EM Exit, but sounds are defined to RND Exit.

As far as I can see, I can confirm this!

• There are only two kinds of Steel Wall defined. (EMC uses 3)

The level editor offers four types of EMC style steel wall -- where did you see two kinds of steel wall where it should be three?

• There is only one kind of Slippery Wall defined. (EMC uses 2)

Yes, I know of only one kind of slippery wall -- do you have an example of an EMC level set and level where there are two different kinds of slippery wall?

• Even though Letter "Copyright" is defined, it's never actually used. (Levelsets instead use Wall

Do you have an example of an EMC level set and level which uses the copyright sign in the original game? Then I can check it in R'n'D.

I've just checked this with an android element placed into the first level of "Ace Mine 1", and the animations for diagonal movement seem to be correct. Which level set and level in the EMC level collection can I check where you have noticed this issue?

That's actually true, some of levelsets has android shrinking and growing animations swapped. And I mean swapped because they are literally swapped: when android moves, for example, to the up left, shrinking animation is growing from the bottom right corner and growing animation is shrinking to the top left.
One of these levelsets with that error is Amiga Mine.

That's exactly what I expected to see when I read Algebroot's initial post, but I just wasn't able to reproduce it. So thanks a lot for a bit more detail on this issue (and the example animation and image) -- I will go and check it with the level sets you mentioned!

BTW: Algebroot, could you please give some hints on some of your other findings as well?

OK, I've debugged and fixed this case (which indeed existed in two different artwork sets). And found another (minor) bug which affects "Forgotten Mine 2" (which used the same (AGA) artwork for ECS and AGA mode).

I hope I will manage to release an update to the Emerald Mine Club collection soon ... which will most probably then contain some more EMC disks which were missing in the currently released package.

It would be also better to convert all PCX files to PNGs after the support of more image file types was added to optimize the size of EMC collection weight. The size of archive will be 3 times lighter than the original one. I just converted "emc_objects.pcx" and "emc_objects.png" and compared their sizes: 55,4Kb and 19,5Kb. Same goes for "emc_players": 11,4Kb and 3,58Kb and others.